Flat-6 engine

A flat-6 is a 6 cylinder configuration of a flat engine. The cylinders are laid horizontally, with three on each side. The movement of the pistons in a horizontal engine is all in the same plane, so it creates less vibration than in a V-configuration engine; particularly one with an odd number of cylinders on each side of the engine, like a V6.

Only a few auto makers have used flat-6 engines, among them Tucker in the 1948 Tucker Sedan, Porsche and Subaru. Citroën developed one for the DS but abandoned it due to numerous problems. In the 1960s, Chevrolet made the Corvair with flat-6 air-cooled engines. The shape of the engine suits it better for rear engine designs, where the low center of gravity is an advantage; in front engine designs the width interferes with the ability of the front wheels to steer.

Lycoming developed a very successful series of flat-6 aircraft engines, as used in many Cessna aircraft.

Porsche is well known for its use of flat-6 engines in its Boxster, Cayman, and 911 sports cars. Flat-6 engines are also used in Honda Gold Wing and Honda Valkyrie motorcycles, as well as several Subaru models, including the SVX, Outback, and B9 Tribeca SUV.


The Flat-6 engine of the Honda Valkyrie motorcycle